As far as I know, add_admin_menu_separator isn't a native function at all in WordPress.

I am currently using a custom function called "add_admin_menu_separator" to add a separator one slot before my my menu option, which is to display between "Comments" and "Appearance". However, the separator doesn't get added properly unless there's a third party plugin (ANY third party plugin...) enabled that displays itself at the very bottom of the WordPress menu. I don't understand why it's doing this...